Electric circuit breaker



April 16, 1957 T. R. coGGi-:sHALL 2,789,186

y ELECTRIC CIRCUIT BREAKER Filed May 31, 1955 ELECTRIC CIRQUE? EREAKERThellwell R. Coggeshall, Cynwyd, Pa., as ver Gen eral Electric Company,a corporation of New irorrr Application May 3l, 1955, Serial No. S/2.3

13 Claims. (Ci. 26d-15%) and greater gap separation distance of thecontacts. Furthermore, the physical size and weight et the 1breakeroperating mechanism is ge erally proportional to the size lot thebreaker. Since the size of a breaker and its op rating mechanismdetermines the cost, it is desirable to keep the breaker dimensions at aminimum consistent with proper performance.

A principal yobject or" this invention is to provide a compactarrangement of the various elements of an impulse-type circuit breakerand its operating mechanism.

Another object `of this invention is the provision of an improvedcircuit interrupter of the impulse type wherein the operating mechanism,the impulse means, and the contacts are disposed coaxially in a verticaldisposition so vas to minimize the amount cf floor or ground spacerequired for the breaker.

Still another object is to provide for an electric circuit breaker animproved compact fluid-actuated operating mechanism which is capable orproviding rapid and ellective trip-free opening operation.

According to one form of the invention, an electric circuit interruptoris provided with a reciprocably movable rod-like Contact, impulse pistonand cylinder means, together with fluid actuating means, all of whichelements are coaxially disposed and contained within a continuousenclosing structure. According to another feature of the invention aquick-release latched-closed dump Valve of large pressure-release areais characterized by having but a relatively small actuating surface areawhich is exposed to the iluid pressure supplied to the operatingmechanism for the circuit breaker. Because of this small actuatingsurface a sensitive high-speed latch, or prop, can be, and is, used forholding the dump valve closed against the force of said fluid pressure.Thus, when the latch receives an operating impulse, say during theperformance of a circuit breaker closing operation with a fault presenton the line, it causes the valve quickly to open suitable dumping ports.This produces an immediate collapse in the iluid pressure within theoperating mechanism and thereby enables appropriate energy-storing meansto impart an advantageous quick reversal to the circuit breakeroperating parts.

The invention will be better understood from the following descriptiontaken in conjunction with the drawing in which Fig. l is across-sectional view of an interrupter and its `operating mechanismembodying the invention with the parts shown in the closed position ofdtates Patent the breaker; Pig. Z is a cross-sectional View of the lowerportion of Fig. l with the moving parts shown transiently with thebreaker almost open and with the dump valve about to reset; while Fig. 3shows these parts in their positions of rest which they will occupy withthe breaker in its fully open circuit position.

Referring new to Fig. l, l provide a metallic base-plate l on which ismounted porcelain shell sections 2 and 3 which together form anenclosing structure for the circuit breaker. A gasket 6 of resilientinsulating material such as rubber is interposed between the base-plate1 and the ceramic shell 2. Similar insulating gaskets 7 and 8 areinterposed between the ceramic shells 2 and 3, while still anotherinsulating gasket 'l is mounted be tween the upper end of shell section3 and metallic closure structure generally designated by the numeral 12.

The structure described thus tar is maintained sealingly in compressionby means or a mechanically strong insulating tubular casing 13 which isshown sealingly secured to the base member l at its lower extremity byan internally threaded collar Likewise, the upper end of the casing i3is shown secured to the upper closure structure l2 by the bolted collarstructure l5. The tensional tubular casing i3 and the compressionalporcelain shell elements 2 and 3 are maintained in constant resilientrelationship through the interaction of an annular series of yicldablecompression springs i6 which bear against an annular plate whichtelescopes sealingly within the cylindrical 'llange of the closurestructure l2 as shown.

lt is preferable to avoid tree communication between the contaminableinterrupter oil lilling the interior of casing ll: and the purelyinsulating oil for the ceramic shell surrounding the casing i3. To thisend, the ange portion ot the structure l2 serves as division barrierwhich permits two oil levels to be maintained, that ot the interrupter(which is indicated as oil level A) lying above the flange structure,and that of the shell (indicated as oil level E) lying within the angestructure. However, oil from both sides of the casing i3 may be drainedout through the drain passage indicated by the numeral 17 which is shownin communication with the inside of the casing l and with the annularspc' the casing and the weat. erproc;E 2 and 3.

between insulating shell sections nel;

a 'per and a lower terminal, t d g indicated at iS, while the upperterminal is in le Le f the numeral and t et l is electricallyconnect/eil by brazing or weldinlg1 strdlslt; e inteffral with theclosure member Terminal 1S is an extension of an a e structure 2l), aor" which is clamped between the insulating gaskets 7 and and having theupstand ig perdon thereof electric-ally connecte to the interr structureby a plu- J'nc studs 2da which e rd sealingly c .ngs to. ed within thecasing and which,

nular bellows ducting sleeve 2l. Sleeve El its t fuer e or other securedto a conducti pla forms an electrical connection through the agency of'c prermd Contact lingers 2.3 with the reciprocably metallic rod contact24. movable rod :et in turn cooperates, for drawing the arc to beeminguished, with an upper set of lixed linger contacts "5 disposedtulighion about the conducting stud 26 which is secured within the hubportion 27 of the closure member t2. Hub portion 27 is supported by aspiderlike structure Ztl which, attached to the member 12, thus is inelectrical contact with the upper terminal 19.

When the rod-like contact 24 is drawn downwardly and separates from thecontact lingers 25, an arc is.

nd is welded te 22 whichl er ends, connect to tie internal metalliccon-- drawn therebetween and within the interruptor structure generallydesignated by the numeral 29. Since the details of this interruptorstructure form no part of the present invention, it is believedsufficient merely to say that the interrupter unit 29 comprises aplurality of battle plates constructed of insulating material suitablyapertured to define an interrupting chamber through which the rodContact 24 is reciprocable. The interrupting chamber is also providedwith lateral openings permitting arc-extinguishing fluid to flow thereacross and eX- tinguish the arc, as will soon appear more clearly.

The lower extremity of the rod-like contact 24 is threadedly secured toan insulating operating rod 30 at the lower extremity of which ismounted piston member 3i. iston 3l is reciprocable within the enlargedlower end of an insulating sleeve 32. A metallic extension of the woodenoperating rod 3d is indicated at 33 and the lower extremity thereof isprovided with a roller 3d which engages a prop-type latch member 3S tomaintain the rod Contact 24 in the closed circuit position. Contact 24is biased toward the open position by gravity and by means of acompression spring 36 which encircles the rod 33. Thus, upon clockwisemovement of the prop or latch about the axis of its pivot shaft 37, therod contact 24 separates from the finger contacts 25 due to gravity andto the downward force of biasing spring 36.

VFor the purpose of ensuring the extinguishment of the arc produced whenthe contact 24 is withdrawn downwardly through the interrupting unit 29,a blast of liquid dielectric is forced transversely across theinterrupter unit comprising the baffle stack 29. The structure fordirecting and supplying this impulse or blast of fluid across the lowerportion of the baille stack 29 comprises a tubular conduit 38 which isthreadedly connected at its upper end under the baffle stack by anadapter element 39 (which preferably houses a schematically-shownnonreturn valve), the conduit 38 telescoping into a reciprocablyVmovable cylinder 40 operative about a xedly mounted annular pistonmember 4l. When in the charged position as shown, the movable cylinder40 is biased downwardly by means of the compression spring 42 which atits upper end engages the fixed piston 41 which is supported on one sideby one or more of the abovedescribed blast eonduits 3S and on the otherby a corresponding number of counter-poise cylinders 43 of the samediameter, which elements are maintained immovably between the fixedpiston and the conducting plate 22. The upper end of the movablecylinder 4G is substantially sealed by means of a cover plate 44 whichis provided with suitable packing for preventing unnecessary wastage ofthe impulse blast of arc-extinguishing liquid which must usefully flowthrough the conduits 38. The strong insulating thrust tube 32 for thecylinder 40 is provided with a lower bored portion 46 which constitutesan operating cylinder for the contact-actuating piston 31 of the contactoperating rod 30. The lower extremity of the impulse thrust tube 32 isthreadedly secured in the large reciprocally movable piston member 47which is slidable within a main operating cylinder 4S.

For the purpose of preventing the leakage of fluid through thebase-plate 1 in the opening through which the rod 33 is reciprocable, anappropriate oil seal 53 is provided.

For cooperating with the blast tubes 38 and counterpoise spacers 43 inthe support of the fixed piston 4l, a metallic cylinder 54 abuts at itsupper end the piston 41 while its lower end is screwed into a fixedplate 5S which in turn stands upon the supporting members 56 which aremounted on the base-plate 1.

v From the above, it will be understood that with the breaker in thecontact-closed impulse-charged position shown in Fig. 1, the hold-closedlatch or prop 3S supports the-rods 33 and 3!) whosepiston 31 in turnsupports (at the upper end of the bore de) the thrust tube 32 which,through the upper end cover of the impulse cylinder 40, transmits thisholding action or effect in opposition to the downward bias of the heavyimpulse spring 42. In addition, the hold-closed prop 35 acting throughrods 33 and maintains the contact 2d in closed position against the biasof the contact opening spring 36.

Thus, when the latch 35 is tripped, the rod 33, the rod 3Q and contact2d descend under the action of the biasing spring at high speed to drawthe interrupting .l in audition, the movable cylinder 46 is forced diybut independently and at a slower rate clue to the oil-compressingaction of spring 42. Accordingly, the faster-moving piston 3i will havemoved out of engagcrnent with the shoulder of the bore 46 of theinsulating thrust tube 32. Downward movement of cylinder forces oilcontained in the space 49 above the fixed piston il to be forced fromthe space 49 through the ports Sil, upwardly through the conduit orconduits 3S, across the are in the bafile structure 2%, after which itvents upwardly as indicated by the arrow 51 and through the ampleperforations 52 formed in the closure plate 23. Such a cross-blast ofliquid dielectric effectively aids in extinguishing an arc drawn betweenthe upper end of the rod contact 24 and the finger contacts 25, as iswell known in the art.

y)During the above-described opening movement, it will be observed thatthe downward contact opening stroke D is substantially longer than theimpulse stroke E, as indicated in Fig. l; for at the end of the strokethe large impulse movable cylinder 4t) and its operative piston 47 hasbeen arrested by the buffer resting on the supporting member 55, whilethe contact piston 31 has continued downward to the point where itsroller 34 finally rests against a suitable stop such as shown at 56a inFig. 3.

yIn order to close the interrupter, and to charge the opening andimpulse piston springs, fluid pressure is supplied through a conduit `57to the space within the cylinder 48 to exert an upward forcesimultaneously on both the small piston 3f. to close the rod contact 24and on the large piston 47 to raise the movable cylinder 40 to its upperspring-charged position through theimpulse thrust tube 32. As is wellknown, a suitable pressure reservoir and control Valve means would beutilized to supply fluid pressure through the conduit means 57 to thecylinder 48. Preferably, the fluid for operating pistons 31 and 47 wouldbe air under pressure.

Should an arc of fault proportions strike between the finger contacts 25.and the rod contact 24 at an instant just before the parts reach theclosed position, it is desirable to have `the breaker trip itself freein which event the rod contact `should rapidly reverse toward openposition with the impulse means comprising cylinder 40 and the Xedpiston 41 available for immediate use. In order for these elements toreverse motion quickly, it is necessary to relieve the fluid pressurewithin cylinder 48 promptly. To this end, the cylinder is provided withlarge dump ports 58b which are normally closed olf by means of a dumpvalve 58 comprising a sleeve portion ditting about the cylinder The dumpvalve 58 has a piston-like portion which surrounds the operating rod 33and has an actuating surface 58a which is exposed to fluid pressurewithin the cylinder 48. The actuating surface 58a has a relatively small(area in comparison to the large cross-sectional area of the cylinderand of the dumping' ports 58h, and, as a result, the pressure forcestending to drive the valve 58 downwardly in-to an open position arecomparatively light. This is advantageous, in that it permits me to usea sensitive highspeed latch, or prop, for holding the high-capicity dumpvalve 58 in closed position. Such a prop is shown at 59 cooperating witha suitable latch roller et). When this prop 59 receives lan operatingimpulse, say in respouse to the breaker being closed on a fault, it 'i'sca.-

pable of responding at high speed, i. e., unlatching, to permit the dumpvalve 58 quickly to open under the force of pressurized fluid in aidcylinder. This permits fluid pressure within the cylinder 48 rapidly tocollapse so that the pistons 47 and 3l are free to move downwardlyrapidly against negligible Iback pressure under the released force oftheir opening springs.

After the dump valve 58 opened to permit collapse of the fluid pressurein the cylinder 48, it will be restored to its normal or closed positionby means `of the spring 36, which serves not only as a contact openingspring but also as a dump valve resettincy spring. The dump valve 53will then be held in its closed position by the valve-controlling prop59, as will soon be more apparent.

Referring to Fig. l, the valve prop 59 is provided with a latch face soinclined that the downwardly-'acting iluid pressure forces urge the proptoward its released position against the bias of a suitable resettingspring 59a mounted about the pivot of the prop. This valve prop 59 isnormally prevented from moving into its released position by means of `asecondary latch 6l which cooperates with an undercenter toggle coupledto the prop. This toggle comprises a pair of pivotally interconnectedlinks 62 and 63 carrying at their knee a latch roller 6ft which isnormally supported on the secondary latch 6l. The toggle link 63 ispivotally supported on a iixed pivot pin 63a and the toggle link 62 ispivotally joined to the prop 59.

rl`he contact prop 35 likewise is provided with a latch face so inclinedthat the opening spring 36 urges the prop 35 toward its releasedposition against the bias of a suitable resetting spring 35a. The propis normally prevented from moving into its released position by means ofanother secondary latch 67 which cooperates with an undercenter toggle65 corresponding to the previously-descri-bed toggle 62, 63,

The two secondary latches 61 and 67 are coupled together forsimultaneous tripping by a linkage 7d which, together with the secondarylatches, constitutes a master latch assembly which is operable by asingle tripping solenoid 7l. T his tripping solenoid '71 is suitablyconnected by means (not shown) to be responsive to abnormal currentconditions in the breaker power circuit. The linkage 7d comprises .atripping crank 72 pinned to the rotatable shaft 73 of latch 61. Anothercrank 74 pinned to this shaft 73 is pivotally joined to a connectinglink IS having a lost motion slot 75a at its lower end. This lost motionslot 75a receives a pin 76 carried by another crank 77 which is pinnedto the shaft of the secondary latch 67.

Thus, when the tripping solenoid 71 is energized, as from abnormal lineconditions, it drives the tripping crank 72 counterclockwise trippingthe valve-controlling latch 6l. Such movement of trip crank 72 alsoturns crank 74 and lifts the connecting link 75 thereby tripping thecontact controlling latch 67. When the valvecontrolling secondary latch61 is tripped, the toggle 62, 63 is free to collapse and the valve prop59 to release under the influence of downwardly-acting luid pressureforces transmitted through the roller 6?. Thus, if pressurized uid isthen present in the cylinder 48 it will force the dump valve open andquickly exhaust through ports 58h thereby permitting the then-unlatchedpistons 3l and i7 to move rapidly downwardly against negligible backpressure within cylinder 48, whereby to produce rapid breaker-openingmovement.

lln the event that this circuit breaker' opening movement was a normalswitching-open operation, the dump valve prop 59 would not haveresponded because, although the secondary trip latch 6l had moved outfrom under the toggle-knee roller 64, no downward force would have beenapplied to the dump valve 'to overcome the upward forcethereupon exertedby the upper end of the spring 36, and because the latchs reset spring59a would have kept the toggle links 62 and 63 extended (in the Fig. 1position). The reason that no downward force would have been applied tothe dump valve is that pressurized iluid within cylinder 48 wouldpreviously have been exhausted to atmosphere by the usual control valve(not shown) which normally vents the cylinder to atmosphere except whenoperated to supply fluid to the cylinder 4S.

Thus, for a normal opening operation, it will be understood that onlythe main prop 3S would respond to the tripping or' secondary latches 61and 67 and that the breaker would open while the dump valve would remainundisturbed during this spring-operated breaker opening operation.

As soon as the tripping solenoid 71 is deenergized, thevalve-controlling secondary trip latch 61 can reset immediately throughthe agency of its reset spring 61a. The lost-motion slot 75a in the link75 permits the latch 61 to reset independently of the other secondarylatch 67 which may reset independently at any time because of its ownreset spring 67o. With the breaker now in its open position, i. e., withthe roller 34 now occupying its lowermost position, which is shown inFig. 3, the main prop 35 will have resumed its reset position under theiniluenceof its own return spring 35a.

Consequently, in response to a subsequent closing operation whenpressure air is admitted to cylinder 4S through conduit 57, the breakercontacts will be reclosed through stroke D, and the impulse spring 42will be recharged through its shorter stroke E, .as the small and largepistons respectively move upwardly. it will be observed that theshoulder formed at the upper end or bore 46 interconnects thecontact-controlling piston 31 and the impulse-charging piston t7 formovement in unison near the end of the closing stroke. This etectivelyinsures that the impulse means fdl, ft2 will be fully charged at thetime the contact closing stroke is completed, thereby insuring that theimpulse means will then be prepared for a fully rated operation in caseimmediate reopening is necessary.

En this upward closing stroke, the roller 34 will have to move past thenow reset main prop in so doing, it will have once more to break itstoggle 68. To enable this to take place, provide a cam-like extension 8ifor a latch crank 82, which, like prop 3:3', is free to rotate aboutshaft 37. At its other end, the crank S2 is pivotally connected to anactuating link 33 which has a lost-motion connection with thecontact-controlling secondary latch 67. The extension d is located so asto be in interfering position with respect to the roller 34. As aresult, when the roller 314i moves upwardly during a closing operation,it encounters extension rotates crank 82 clockwise, pulls link 53downward, thereby pulling the secondary latch 67 out from under itstoggle roller so that the toggle 63 now may collapse as the contactroller 34 brushes past the main prop d temporarily displaces it to theright. prop 35 1 nitly resets under the roller 3d (as the latter assumesits fully closed position 'he influence of its return spring 35a. alsoresets at the sonic time under the bias of its return spring 67a.independence between these resetting movements is provided by means ofthe lost-motion connection iid between link d3 and the secondary latch67. rthus, inertia or ound forces on tbe prop 35 and the latch 67 do notcommunicate one with another to impede the fast resetting speed of theprop land latch.

Assuming that no line fault was present during this closing stroke,pressure has been exerted downwardly upon the surface 5tlg of the dumpValve S8, but, because the tripping solenoid 7l has remained11n-energized, the dump valve is held closed by the prop-latch 59. Atthe end of the closing stroke, the cylinder 4S exhausts in the usualmanner through its conventional control valve (not shown) which hadpassed pressure air to the cylinder through the of Fig. l) undlzonduitf? when opened but 'had `exhausted yto atmosphere when closed.

lf now, on :the 'other hand, Athe breaker should close on a faultedline, `the tripping 'solenoid 7l would become energized, possibly beforeVthe end jof the upward stroke or" the Contact piston 31. Consequently,both props 35 and '59 would 4be released in such a case; for now thedownward pressure on the face SSaof the vdump `valve 53 would lcauseroller foil Ato sweep latch 59 vfrom out of its path, for the reasonthat the downward pneumatic force on valve face 522:1 is greater thanthe upward force of spring 36. Accordingly, the dump valve will movedown .through its travel distance -C where it will be arrested by, say,an abutment 85 as is clearly shown in Fig. 2. With the dump valve inthis open position, it is apparent 'that the residual pressure below thealmost closed piston 47 is instantlyr evacuated through the ports :5S-bso that the moving Contact structure can open unimpededly down- Ward,leven through the control valve (not shown) may still be feedingpressure air through the conduit 57. Thus, the dumping valve arrangementof lmy invention, having a large escape port area and a small integralpiston `area provides a very eiiective way of permitting instantreversal of the closing members of the circuit breaker in the event of atrip-free operation resulting from closing on a faulted line.

Fig. 3 shows the tripped-open condition to which the breaker andmechanism return after experiencing either a trippinf7 operation fromthe closed position of Fig. l or a trip-free operation shown commencingas in Fig. 2. ln the position of Fig. 3, it will be observed that bothpistons 3l and 47 are down and the dump valve 58 has een returned to itsclosed upper position by the upward bias oi spring 36. Also the Contactroller 34 is in its lowermost position due to the downward bias of thespring 35.

lt will be understood that although my disclosed mechanism permits theuse of a single compression spring 36 for controling dumpvalve-resetting and contact-opening, the single spring 36 could bereplaced by two separate springs, one spring for biasing the rod 33 andassociated parts downwardly and another spring for maintaining the dumpvalve 5% in its normally closed position, For eX- ample, a iisedstructureV could be arranged so as to surround the rod 33 and one springcould have its upper end engage the dump vaive S9 and its lower end bearon the lixed plate, while another spring could engage the shoulder @ilon the rod 33 and its upper end could engage the lower surface of thefixed plate.

While l have shown and described particular embodit ments or" theinvention, l do not wish to be limited thereto and intend in theappended claims to cover all such changes and modifications as fallwithin the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

l. A liuid actuated operating mechanism for an electric circuit breakerhaving a biased-open latched-closed movable contact and having impulsemeans normally occupying a position corresponding to the closed positionof said movable contact and movable to an operated position upon openingor" said movable contact for supplying liquid dielectric to the arcdrawn thereby, said mechanism comprising a cylinder, means for supplyingpressure liuid to said cylinder, a :First piston operatively coupled tosaid movable Contact and movable in response to pressure liuid saidcylinder for imparting closing movement to said Contact, and a secondpiston operatively coupled to said impulse means and movable in responseto pressure iluid in said cylinder for moving said impulse means to itsnormal position.

2. The mechanism of claim l in combination with meansinterconnectingsaid pistons formovement in unison near the end of a`closing stroke Yfor insuring that `8 fs'aid-im'pulse-meansisreturne'dto its normal position when 'said contact is inclosed'positio'n.

3. An electric circuit "interrupt-er comprising a reciprocably movablecontact, impulse means including a piston and cylinder and operable tosupply liquid dielectric to the arc drawn by said contact upon openingmovement thereof, said contact and said impulse means beingsubstantially coaXially disposed, latch means for holding said contactin its closed position and for holding said impulse means in a normalposition corresponding to the closed position of said contact, biasingmeans `for producing opening 4movement of said VContact upon release ofsaid latch means, means for operating said impulse means upon release ofsaid latch means, a lluid motor including two coaXially disposed pistonsoperable from pressure fluid supplied to a common cylinder, means foroperatively connecting one of said pistons with said contact and the'other of said pistons with said impulse means, and means for supplyingpressure liuid to said motor to operate said ypistons thereby to causeclosing movement of said contact and movement of said impulse means toits normal position.

4. An Velectric circuit breaker comprising a biasedopen latched-closedreciprocably movable rod contact, reciprocable impulse means normallyoccupying a posi- 'tion corresponding to the closed `position of saidmovable contact and movable to an operated position upon opening of saidmovable contact for supplying liquid dielectric to the arc drawnthereby, said contact and said impulse means being coaxially disposedwith said contact 'being reciprocable in an opening through said impulsemeans, an operating'cylin'der, said cylinder and said contact beingcoaxially disposed, means for supplying pressure fluid to said cylinder,a first piston movable with said movable contact and operable inresponse to pressure fluid in said cylinder for imparting closingmovement to said contact, and a second piston movable with said impulsemeans and operable in response to pressure uid in said cylinder formoving said impulse means to its normal position.

5. An electric circuit breaker comprising a biased-open latched-closedreciprocably movable rod contact, recipro- Ycable impulse means normallyoccupying a position corresponding to the closed position of saidmovable contact and movable to an operated position upon opening of saidmovable contact for supplying liquid dielectric Vto the arc drawnthereby, said contact and said impulse means being coaxially disposedwith said contact being reciprocable in an opening through said impulsemeans, an operating cylinder, said cylinder and said contact beingcoaxially disposed, means for supplying pressure fluid to said cylinder,a first piston movable with said movable contact and operable inresponse to pressure fluid in said cylinder for imparting closingmovement to said contact, and a second piston movable with said impulsemeans and operable in response to pressure luid in said cylinder formoving said impulse means to its normal position, said pistons beingsubstantially coaxially disposed.

6. A fluid actuated operating mechanism lforan electric circuit breakerhaving a biased-open laitched-closed movable contact and having impulsemeans normally occupying a position corresponding to the closed positionof said movable contact yand movable to an operated position uponopening of said movable contact for supplying liquid dielectric to thearc drawn thereby, said mechanism comprising a cylinder having a dumpingport in a wall thereof, means for supplying pressure fluid to saidcylinder, a dump valve normally closing said port and having a surfaceexposed to pressure fluid in said chamber, latch means for holding saidvalve in its normal position, the force exerted by thepressure fluid insaid cylinder on said surface being effective to move said valve to anoperated position thereby to open said port in response to release ofsaid latch means, a first piston operatively related with said movablecontact and movable in response to pressure fluid in said cylinder forimparting closing movement to said contact, and a second pistonoperatively related with said impulse means and movable in response topressure iluid in said cylinder for moving said impulse means to itsnormal position.

7` In an electric circuit breaker comprising a movable contact and meansbiasing said contact toward open position, an operating cylinder havinga dumping port, piston means operable by pressurized fluid supplied tosaid cylinder for imparting closing movement to said contact, a dumpvalve normally closing said port and having an actuating surface exposedto pressurized fluid in said cylinder, rst prop means operable whenlatched to hold said dump valve in closed position and operable whenunlatched to permit said dump valve to open under the force ofpressurized lluid in said cylinder, second prop means operable whenlatched to hold said contact in closed position and when unlatched topermit opening of said contact, master latch means normally maintainingboth of said prop means in latched position and releasable to causeunlatching of both of said prop means, a single tripping solenoidoperable to cause release of said master latch means whereby to causeopening of said dump valve and said contact, means operable while saidcontact is in open position for returning said dump valve to closedposition, and means operable thereafter for restoring said rst propmeans to its latched position thereby holding said dump valve closed sothat pressurized fluid can then be applied to said cylinder to impartclosing movement to said contact.

8. The mechanism of claim 7 in which said contact biasing means and saiddump valve restoring means comprises a single spring acting between saiddump valve and said movable contact.

9. The mechanism of claim 7 in which said master latch means comprises apair of trip latches for respectively holding said prop means in latchedposition, and a linkage interconnecting said trip latches and operableby said solenoid to cause substantially simultaneous tripping of saidlatches.

l0. The mechanism of claim 7 in which said master latch means comprisesa pair of trip latches for respectively holding said prop means inlatched position, and a linkage interconnecting said trip latches andoperable by said solenoid to cause substantially simultaneous trippingo1 said latches, said linkage comprising a lost-motion connection forpermitting independent resetting of said trip latches into theirrespective holding positions after tripping thereof.

11. In an electric circuit breaker comprising a movable contact andmeans biasing said contact toward open position, an operating cylinderhaving a dumping port, piston means operable by pressurized fluidsupplied to said cylinder for imparting closing movement to saidcontact, a dump valve normally closing said port and having an actuatingsurface exposed to pressurized uid in said cylinder, rst prop meansoperable when latched to hold said dump valve in closed position andoperable when unlatched to permit said dump valve to open under theforce of pressurized uid in said cylinder, second prop means operablewhen latched to hold said contact in closed position and when unlatchedto permit opening oi said contact, master latch means normallymaintaining both of said prop means in latched position and releasableto cause unlatching of both of said prop means, a single trippingsolenoid operable to cause release of said master latch means whereby tocause opening of said dump valve and said contact, means for returningsaid dump valve to closed position after opening thereof, means operablewhile said contact is in open position for restoring oC-th of said propmeans to latched position whereby to hold said dump valve closed, meansresponsive to contact-closing movement for temporarily displacing saidsecond prop means without disturbing said first prop means, and meansfor thereafter restoring said second prop means to its latched positionin response to completion of said closing movement whereby to hold saidcontact closed.

l2. Operating mechanism for an electric circuit breaker comprising anoperating cylinder having a peripheral wall containing a radiallyextending dump port, means for supplying pressurized fluid to saidcylinder, piston means operable by said pressurized uid for actuatingsaid breaker, an axially movable dump valve iitting about said wall andnormally closing said port, said dump valve having an actuating portionexposed to pressurized fluid within said cylinder, the eiective workingarea of said actuating portion being only a minor fraction of the crosssection area of said cylinder, and latch means normally holding saiddump valve closed and operable when released to permit said valve toopen under the force of pressurized uid in said cylinder.

13. In a Huid-actuated operating mechanism for an electric circuitbreaker having a movable contact biased toward open position, anoperating cylinder, rod means extending through an end Wall of saidcylinder and operatively connected to said contact, a piston coupled tosaid rod means and movable in response to pressure tluid supplied tosaid cylinder for imparting closing movement to said contact, saidcylinder having a radial dump port in a peripheral wall thereof, anaxially-movable sleevetype dump valve fitting about said cylinder andnormally closing said port, said valve having an actuating portionsurrounding said rod means and including an actuating surface exposed topressure iluid in said cylinder, and releasable latch means for holdingsaid valve in its normal position, the force exerted by the pressure uidin said cylinder on said actuating surface being effective to move saidvalve to an operated position in which said dump port is open inresponse to release of said latch means.

References Cited in the file of this patent UNITED STATES PATENTS1,728,829 Hilliard Sept. 17, 1929 2,286,023 Strang June 9, 19422,420,872 Easley May 20, 1947 2,566,095 Scarpa Aug. 28, 1951 2,578,204Peek Dec. 11, 1951 2,578,349 Goodwin Dec. 11, 1951

